Native trees at Westonbirt

Compared with other countries, Britain has relatively few native trees; between 30-40 (the exact number depends on how you define a 'tree' and 'species').

Westonbirt has a native tree collection located in Silk Wood, where you can see most of Britain's native tree species.

Westonbirt's '2000 year old lime'

Westonbirt Arboretum is home to one of Britain's oldest trees, a small-leaved lime which has been managed as part of a coppice rotation dating back centuries.

The lime is now managed on a 20 year rotation and was coppiced in November 2012.

A mix of traditional and modern techniques was used to coppice – cut back to stumps - around 60 lime stems that had grown from one original specimen thought to be hundreds, possibly thousands, of years old.

The work took place using a combination of traditional and modern techniques, combining the use of bow saws, Japanese saws and chainsaws

DNA tests carried out on the lime in the 1990s (at the time of the last coppice rotation) showed the clump of limes to originate from one tree dating back centuries.

The practice of periodic coppicing has allowed the tree to live for this long. Shoots form new stems (or stools) once the clump has been cut back. The lime at Westonbirt Arboretum is coppiced every 20 years.

The lime can be found near to Maple Loop and the National Japanese Maple Collection, found in Westonbirt Arboretum’s Silk Wood.

A large-scale sculpture was commissioned using the coppiced timber to take the place of the coppiced stems whilst they regrow.

The native tree timeline

About 25,000 years ago, the last Ice Age was at its peak with ice sheets covering much of northern Britain - only a few specialised plants could survive in the bleak tundra landscape.

At this time, the species we now consider to be Britain's trees and shrubs were confined to warmer regions of southern Europe, such as northern Spain and the Balkans.

Between 10,000 and 5,000 years ago, many familiar native trees and shrubs re-colonised Britain from southern Europe.

Aspen and rowan rose to early prominence along with Scots pine, wych elm, pedunculate and sessile oak, small-leaved lime, alder ash, and field maple; as well as many of our native shrubs.

Around 5,000 years ago, Neolithic farmers began to clear forests for pasture and growing crops. By the early Iron Age, it is estimated that between one-half and two-thirds of England had ceased to be forest.

By the time of the Roman invasion, Britain was probably not much more wooded than today.

The period of Roman occupation of Britain marks the beginning of a continuing tradition of importing species from abroad. The Romans are often credited with introducing sweet chestnut and walnut to Britain and the remains of nuts of both species are found on archaeological sites.

How do we date Britain's native trees?

Much of the our understanding of the development of our native trees comes from the study of the pollen grains and spores that become incorporated and preserved in the sediments at the bottom of lakes, and in peat bogs.

Careful counting and analysis of the number of grains of different species is used to build up a reconstruction of the surrounding vegetation that existed when the pollen was dispersed.

By comparing the date that a particular species of tree first appears in pollen cores taken from a range of sites across Britain, scientists can work out the time when it first appeared in Britain, and its direction and rate of spread across the country.

DNA technology has allowed the distribution of particular genetic markers amongst individual trees in different populations to be compared. In cases where physical or scientific evidence is unavailable, circumstantial evidence is used to support or contradict when a species may have arrived.